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Introduction to the characteristics of thermally conductive adhesives and the common terminology of thermally conductive adhesives


Introduction to the characteristics of thermally conductive adhesives and the common terminology of thermally conductive adhesives

Modern computers generate heat that is mainly emitted through the upper surface of the component, so it is important to have low thermal resistance in the connection area, which is associated with the proper operation of the heat sink. LEDs are favored by the majority of users for their small size, low power consumption, environmental friendliness, robustness, and rich color of the light source. However, one of the bottlenecks facing the development of LED lighting is heat dissipation, which can be solved with a thermally conductive adhesive.

Advantages of thermally conductive adhesive

1, the use of thermally conductive adhesive can improve the performance of the heat sink. When the glue is applied reasonably, the thermally conductive adhesive fills the gap between the heat sink and the heat source. The gap must be filled. If the glue is not filled, the heat is prevented from escaping and has to be repaired or replaced at great expense.

2. Bonding the radiator with a thermally conductive adhesive ensures the stability and reliability of the required temperature and technical parameters. For example, it is practically possible to achieve the desired result without degrading the bonding surface, brushing the surface with glue and catalyst. In addition, the heat-conductive adhesive is easy to use, self-leveling, and does not require pre-treatment of the surface, therefore, product costs and application time are substantially reduced.

3. Fast-curing two-component thermally conductive adhesives can effectively bond electronic components and heat sinks without mechanical devices. These acrylate structural adhesives have a substantial cost advantage over mechanical fixing devices, and this frequent need for positioning during production and assembly often adds up to additional costs. Firmly bonding the components with room temperature curing thermally conductive adhesives not only cools the vertical surfaces but also cools the metal housing and side panels, which are not fitted with chips, screws, or other mechanical positioning devices. The acrylate thermal conductive adhesive can also replace mechanical devices and silicone grease that causes contamination.

4. Some electronic components, such as master video processors, cannot be perforated or fitted with clamps and rivets to hold the heat sink in place. Thermal adhesives are the ideal solution in this case. The adhesive not only provides the mechanical strength of the bond between the heat sink and the heat source, but more importantly, it fills all the gaps and excludes the air between the parts (thermal insulation).

5. The thermally conductive adhesive can also bond many types of material, even on dirty or greasy surfaces where grease is required, and a 10 g vibration test shows that the bond has no adverse effects. The thermally conductive adhesive also has a high peel strength and a high impact strength, which makes the bond firm, durable, and resistant to vibration. After extensive ambient temperature and humidity testing and aging tests, this thermally conductive adhesive not only fully met the requirements, but in fact, far exceeded the basic properties of tensile strength and thermal conductivity originally envisaged.

 Traditional applications for thermally conductive adhesives for packaging include chip soldering, microelectronic packaging for mounting heat sinks, sensor packaging. In addition, with the development of electronic and electrical engineering, LED lamps, solar devices, heat exchangers, and automotive components, more and more new power electronics have different needs than ever before. Thermally conductive adhesives have a wide range of applications for these products, meeting not only different mechanical properties but also unique requirements and challenging process parameters, such as adhesives joining components with mismatched thermal conductivity.

 Commonly used classifications of silicone thermally conductive materials

1, Thermally conductive silicon film (also called thermally conductive silicone mat, thermally conductive silicone film)

With good thermal conductivity and a high level of pressure resistance, it meets the current demand for thermally conductive materials in the electronics industry and is the best product to replace the binary heat dissipation system of silicone grease thermal conductive paste plus mica sheet. It is the best product to replace the binary heat dissipation system of silicone grease and mica sheet. The product is easy to install, facilitates automatic production and product maintenance, and is a new type of material with great technical and practicality.

The thickness, softness, and hardness of the thermally conductive silicone film can be adjusted according to the design so that the thermal conductive channel can be bridged in the thermal structure, the chip, and other size differences, reduce the structural design of the contact surface of the radiator parts of the work difference requirements, especially for the flatness, roughness of the work difference, if the processing accuracy is improved will largely increase the cost of the product, so the thermally conductive silicone film can fully increase the heating body and radiator parts The contact area of the heat sink can be fully increased and the production cost of the heat sink can be reduced.

2, thermally conductive silicone grease (also called thermal paste, thermal paste)

It is a kind of white or grey thermal insulating sticky object, which has a certain viscosity, no obvious granularity, non-toxic, tasteless, non-corrosive, stable chemical, and physical properties, and has excellent thermal conductivity, electrical insulation, high-temperature resistance, aging resistance, and waterproof characteristics. Normally, thermally conductive silicone grease is insoluble in water, not easily oxidized, and has certain lubrication and electrical insulation properties.

TSP700 thermally conductive silicone grease also has low oil leaving degree (tends to zero) and very good weather resistance (including high and low-temperature resistance, water resistance, ozone resistance, weather aging resistance, etc.), and can be used for a long time under the temperature of -30℃150℃, even in the temperature above +200℃ can still maintain the wetting of the contact surface.

3Thermal conductive silicone tape

Widely used in the bonding between power devices and heat sinks, can simultaneously achieve the function of thermal conductivity, insulation, and fixing, can effectively reduce the volume of equipment, is a favorable choice to reduce the cost of equipment.

4Heat-conducting silicone tape

It is a silicone polymer elastomer reinforced with glass fiber as the base material, also called thermally conductive silicone cloth, tear-resistant silicone cloth, this silicone cloth can effectively reduce the thermal resistance between electronic components and heat sinks, and electrical insulation, with high dielectric strength, good thermal conductivity, high chemical resistance, can withstand high voltage and metal parts of the piercing and the circuit short circuit.

5Thermally conductive phase change materials

Using the properties of the substrate, a phase change occurs in the working temperature, thus making the material fit more closely to the contact surface, while also obtaining an ultra-low thermal resistance and more thorough heat transfer.

6Thermally conductive fillers (thermally conductive bonding adhesives, thermally conductive potting adhesives)

Used as a thermally conductive adhesive, it not only has the effect of thermal conductivity but also is a thermally conductive material for bonding and sealing potting.

Application of thermally conductive adhesive

1Application in the power supply industry

The power supply industry has a large scope because there are electrical products that have power supply problems. After all, different products require voltage, the current varies. In the early years of solid is to use neoprene (yellow glue) to fix, but the yellow glue is through the solvent volatile after curing, which leads to VOC (VOC is the English abbreviation of volatile organic compounds, usually said in latex paint harmful chemicals to the human body) strange high impact on the environment, temperature resistance is very low, and over time will automatically lose bonding, and silicone thermal conductive silicone and silicone thermal potting adhesive simply These problems do not exist.

2, thermal adhesives in the application of micropower electronics heat treatment

The growth in demand for mobile electronics has brought new design challenges, with increasing emphasis on mechanical strength and heat treatment capabilities. As substrate sizes shrink and operating environments become more complex, integrated product designs must overcome the challenges of heat dissipation while maintaining impact resistance. Thermally conductive adhesives have proven to be an underutilized solution in the heat treatment of power electronics.

 Examples of applications for thermally conductive adhesives

In microelectronic components, practical applications for thermally conductive adhesives are the connection and protection of electronic components such as chip soldering, underfill gluing, encapsulation, and heat dissipation. High-temperature-resistant epoxy adhesives are used in applications that enable the processing of thermally sensitive components so that they can withstand reflow soldering and improve operational stability.

An increasing trend in applications is the mounting of heat sinks for LED chips. Current power LEDs are power-consuming 500 mW per unit, of which only 20% of the energy is converted into visible light. The larger part of the energy must be radiated or dissipated to keep the temperature of the electronics below 120°C. When the temperature rises, the light yield and service life of the lamp are reduced.

The advantage of thermally conductive adhesives for mounting LED chip heat sinks is that they provide mechanical and thermal properties over the entire area of the bond, so that heat dissipation is very effective. The maximum temperature is approximately 66°C. For every 1°C increase in operating temperature, the service life is significantly reduced.

Another application is the encapsulation of temperature sensors or electronic packaging. The thermally conductive adhesive acts as a sealing layer, effectively isolating humidity and conducting heat between the sensor and the environment.

Recently, the demand for new manufacturing concepts for purely electric and hybrid vehicle batteries, cars, and fuel cells has started to grow. This demand can be partially addressed by the use of thermally conductive adhesive bonds. This includes the connection and sealing of power cells, potting of motor components and coils, heating and cooling duct installation, etc.

Similarly, thermally conductive adhesives are often used in the encapsulation of general electrical engineering components, including solar heat transfer devices or heat exchangers. The adhesives replace traditional soldering and brazing methods in mounting and thermally conductive connections, avoiding high thermal loads in processing and subsequent distortion or discoloration. In addition, there are no restrictions in handling combinations of materials such as copper and aluminum which are difficult to process.

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